Climate Change is All About Energy

Climate change is all about energy, a subject familiar to any physicist. Climate changes are driven by changes in the Earth’s energy balance with space, either as the re- sult of variations in the distribution or intensity of incom- ing solar radiation reaching the Earth, the fraction of that radiation that is reflected, or the emission of thermal radia- tion back to space. The greenhouse effect alters the latter, trapping outgoing terrestrial radiation. A reduction in emis- sions during recent decades at exactly the wavelengths where greenhouse gases (GHGs) absorb has been directly measured from space, so there is no question about this effect. Thus the relevant question is how sensitive is the Earth’s climate to changes in the planetary energy balance?